1. Technical Field
The present invention relates to a method of adding a gloss control table for printing an image having a desired glossiness.
2. Related Art
A printing apparatus in which a liquid such as an ink is discharged and printing of an image is performed by a liquid drop (dot) landing on the recording medium, is known. As the printing apparatus, for example, there is an ink jet printer in which a photo-curable ink (for example, a UV ink) is cured by irradiating a light such as an ultraviolet ray (UV) and is discharged. A method is widely known, in which the UV ink is discharged from a nozzle on the recording medium using such ink jet printer, the UV ink dot formed on the recording medium is cured by the irradiated light, and then the UV ink on the recording medium is fixed. (For example, JP-A-2000-158793).
In the method in JP-A-2000-158793, by curing the UV ink dot discharged on the recording medium by the light, an occurrence of bleeds (blur) on the UV ink dots can be suppressed, and it becomes easy to form good quality image.
However, in the image printed by the ink jet printer using the UV ink, there is a problem of unevenness in glossiness occurring. A difference in the amount of ink discharged (also called DUTY) on the recording medium per unit area is considered as one of the reasons for the unevenness in glossiness occurring. That is, there is a difference in glossiness between a portion where the gradation value of the printed image is high and a portion where the gradation value of the printed image is low, and the difference in glossiness becomes uneven. For example, when printing an image of a person's face, at a part such as skin where the gradation value is low and the amount of ink is small (low DUTY), then the glossiness is low. Contrarily, at a part such as a pupil where the gradation value is high and the amount of ink is large (high DUTY), then the glossiness is high. As a result, the unevenness in glossiness occurs depending on the face part, and thus, it is difficult to form good quality image.
As a printing method for improving the unevenness in glossiness described above, for example, in JP-A-2009-218563, a technology is known, in which a desired glossiness of the image can be obtained by adjusting the DUTY of the color ink and the DUTY of the clear ink. In the printing method in JP-A-2009-218563, a gloss control table that defines a relationship between the DUTY of the color ink and the DUTY of the clear ink required for obtaining a predetermined glossiness is created by an experiment in advance, and then, from the gloss control table and the DUTY of the color ink defined by the image data, the required DUTY of the clear ink is obtained.
However, since the relationship between the DUTY of the color ink and the DUTY of the clear ink in the gloss control table varies by the change of the material of the recording medium, as many gloss control tables as the number of types of the corresponding recording media has been needed. That is, in the printing method in JP-A-2009-218563, the printing apparatus (ink jet printer) has to keep as many gloss control tables as the number of various recording media for printing the image in advance. Therefore, to perform the gloss control of the image in printing with respect to the recording medium of which the gloss control table is not kept in the printing apparatus, it has been required to perform a number of test printings or measuring of the test patterns by using the color ink or the clear ink with respect to the base materials of the new recording media, and then obtain gloss control tables corresponding to the new base materials, to store in the printing apparatus.